Contactless data communication has been employed in multiple industries, including the automotive industry. There, contactless data communication is used to gain access to a vehicle. A key or key fob is held by a person and is operable to communicate with a vehicle when the key fob is within range of wireless communication with the vehicle. The person may press a button on the vehicle or lift the handle of a door of the vehicle to initiate communication between the vehicle and the key or key fob. Once communication is initiated, the vehicle and the key or key fob may exchange messages to allow the person access to the vehicle. For example, the key or key fob may transmit one or more authentication messages that the vehicle validates.
One problem that has arisen with contactless data communication is that it is susceptible to a relay attack. In the context of access to vehicles, this attack includes a person initiating the communication with the vehicle by pushing a button on the vehicle or lifting a handle on the vehicle's door. The vehicle then transmits a signal which is captured by the person and relayed to a remote device using a transceiver. The remote device may be located away from the vehicle but in proximity to the key or key fob. For example, the vehicle may be in a parking lot of a restaurant and the owner of the vehicle may be in the restaurant. The remote device may be located inside the restaurant and may relay the signal transmitted by the vehicle in the restaurant. The key fob, while in the possession of the owner, may receive the signal transmitted by the vehicle as a result of the remote device and may respond with authentication signals. The remote device may capture the authentication signals and transmit them to the person in proximity with the vehicle who initiated the communication. The transceiver held by the person may transmit the authentication signals to the vehicle and the vehicle may validate the authentication signals. This may allow an unauthorized person access to the vehicle.